The present invention relates to an improvement of a process for producing kappa-caseino glycomacropeptide, GMP, xcexa-caseinoglycopeptide, CGP or caseinomacropeptide, CMP or a derivative thereof without destroying the milk starting material, in particular whey, which is a useful by-product. This improved process is useful in a industrial scale at commercial way - not just useful in the laboratory.
GMP has numerous useful possible applications.
U.S. Pat. No. 4,994,441 proposed to use GMP in a composition for treating and inhibiting formation of dental plaque and caries, for example in a tooth paste.
U.S. Pat. No. 5,063,203 proposed to use xcexa-caseinoglycopeptide for the manufacture of a composition, in particular a medicament, for the prevention and/or the treatment of thrombi.
Further GMP or CGP has been proposed to stimulate bifido-bacterial growth making it useful in dietetic food products i.a. for infants, and prevention of binding of cholera toxin to its receptor.
GMP has also been suggested for use in the treatment of disorders in amino acid metabolism, such as phenylke-touria (PKU).
Many attempts have been undertaken to find useful processes to prepare GMP. Most of them are not industrially usable.
WO 94/15952 relates to a method for production of a kap-pa-caseino glycomacropeptide i.a. comprising heat treatment of a whey product. This causes a denaturation of the whey by-product so that it will be unsuitable for other purposes.
EP 0 453 782 has proposed a process for the production of kappa-caseinoglycomacropeptide in which the proteins of a whey product concentrated with proteins partly freed from lactose are flocculated, resulting in a precipitate and a first supernatant, and the first supernatant is concentrated by ultrafiltration, leading to a retentate, which is then treated with ethanol, which produces a precipitate and a second supernatant, the second supernatant is collected and then dried. This process is very inconvenient and troublesome.
EP 0 393 850 and U.S. Pat. No. 5,075,424 relate to a process for producing a kappa-caseino glycomacropeptide which comprises adjusting the pH of a solution of milk starting materials containing the kappa-caseino glycomacropeptide to below 4, treating the solution by ultrafiltration with a membrane passing a molecular weight fraction of 10,000 to 50,000, and concentrating the filtrate obtained with a membrane passing a molecular weight fraction of 50,000 or less.
The concentration can be performed on the same filter by readjustment of pH to 4 or higher, typically 6.5, or on another membrane having a smaller cut-off value under 10,000.
This known process has a high production cost, gives an impure product, and the filter is fast fouled during the filtration by protein and must often be cleaned. The process gives a poor yield. A diluted starting solution is used in order to reduce fouling. The diluted starting solution requires use of large amounts of water and more energy. A typical starting solution is a solution having a protein content of 2% by weight.
EP 0 488 589 relates to a process for producing a kappa-caseino glycomacropeptide comprising contacting milk raw materials containing the kappa-caseino glycomacropeptide with an ion exchanger, collecting a fraction which does not adsorb on the ion exchanger, and concentrating and desalting the fraction to obtain the kappa-caseino glyco-macropeptide. This process is rather convenient because it is easy to perform and it does not damage the whey by-product. However deposits on the ion exchanger are a problem, so it has to be cleaned and replaced rather often. The applicant of EP 0 393 850 tries to overcome the problem of protein fouling during filtration by removing proteins by this process using an ion exchanger.
It has now surprisingly been shown that an improvement of the process known from EP 0 393 850 as stated in the following, prevents the drawbacks of the known processes.
The process according to the invention is of the known type which comprises adjusting the pH of a solution of milk starting materials containing the kappa-caseino gly-comacropeptide or derivatives thereof to below 4, treating the solution by ultrafiltration with a membrane passing a molecular weight fraction of 10,000 to 50,000, and after adjustment of pH to above 4 concentrating the filtrate obtained with a membrane passing a molecular weight fraction of 50,000 or less. The process of the invention is characterized in that cold ultrafiltration is applied using a spiral filter.
The process of the invention gives a pure product in a high yield and at a low cost without denaturing the valuable whey by-product. The process gives a better bacteriological control.
Ultrafiltration is preferably carried out at a temperature below 15xc2x0 C., especially 7 to 15xc2x0 C. For the time being it is preferred to use about 12xc2x0 C.
The starting material can be a whey product. It is preferred to use a concentrated whey product, such as a whey product having a content of above 15, especially 35 to 80 and most preferred 85 to 95% by weight protein based on the dry matter content. Preferred whey products are whey protein concentrate, WPC and whey protein isolate, WPI. Consequently is it possible to reduce the amount of energy and water needed in the process
The process of the invention can be carried out using a concentration of 0.8 to 15% by weight of protein , 5 to 15, especially 6 to 8% by weight is preferred. For the time being 7% by weight is the most preferred concentration.
A FV membrane from OSMONICS-DESALINATION, Vista, Calif., USA is a usable membrane. Other firms have corresponding membranes usable in the invention.
The ultrafiltration can be improved by using a filter aid. It is surprising that calcium phosphate can be used, because one should expect that it had a tendency to dissolve in the acid solution. It is preferred to use milk based calcium phosphate, especially if the GMP prepared by the invention has to be used in food or the like.
The ultrafiltration can be carried out at a pH of 2.5 to 3.5, 2.8 to 3.2 being a preferred range, and for the time being a pH of 3.0 is preferred.